Toner for electrophotography, and developing agent, image formation device and image formation method using the same

ABSTRACT

An object of the present invention is to provide an electrophotographic toner which has good fabrication property and excellent developing property, and can form an image having sufficient density and excellent fixing property. As a coloring material for the electrophotographic toner, a black pigment with substantially weak magnetic or non-magnetic property and having a predetermined particle size is used. The electrophotographic toner comprises: a binder resin; and particles containing manganese and iron and having a hematite structure, wherein manganese content is 3 to 30% by weight, an average particle size is 0.01 to 2.0 μm, and saturation magnetization (σs) is 2 emu/g or less, in the particles.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electrophotographic toner forvisualizing an electrostatic latent image formed on a surface of aphotoconductive insulator such as a photoconductive drum in anelectrophotographic method or the like, an electrophotographic developerusing the same, an image forming device and an image forming method.

2. Description of the Related Art

Conventionally, there has been an electrophotographic method as one ofmethods to visualize electric image data on a recording paper or thelike. In the electrophotographic method, an electrostatic latent imageis firstly formed on a surface of a photoconductive insulator (aphotoconductive drum or the like). Then, a monocomponent toner which ischarged by a developing unit equipped with a contact charging mechanismsuch as a blade, and a two-component toner which is charged by beingbrought into contact with carriers, are electrically adhered to theelectrostatic latent image, and the latent image is visualized bydevelopment to obtain a toner image. Further, the toner image istransferred onto a recording paper or the like, and the toner is meltedand solidified to obtain a printed article.

The formation of the toner image on the surface of the photoconductiveinsulator is carried out, for example, by providing uniformelectrostatic charge on the surface of the photoconductive insulator (aphotoconductive drum or the like) by corona discharge or the like,forming an electrostatic latent image by irradiating an optical image onthe photoconductive insulator by suitable means, and then adhering thetoner which has been charged by the electric absorption force of theelectrostatic latent image.

As the toner for developing and visualizing the electrostatic latentimage, there are used particles that are obtained by finely pulverizinga substance obtained by dispersing a colorant, and if necessary, anadditive, such as a charge controlling agent, into a binder resincomprising a natural or synthetic polymer substance or the like, toapproximately 1 to 30 μm.

The fixing method of the toner image transferred onto the recordingpaper or the like includes a method of melting the toner by a method ofpressuring, heating or a combination thereof, and then solidifying andfixing it, a method of melting the toner by irradiating photon energy,and then solidifying and fixing it, and the like. The toner fixed on therecording paper forms a semi-eternal image, and is used as indispensablevisualized information in recent society. Selection of a colorant usedfor the toner at visualization is very important as it greatly affectsimage quality.

Recently, there have been various kinds of electrophotographic images,ranging from monochrome images and mono-color images to full-colorimages. Among these, permeation of full-color images has beenremarkable. However, since it is common for a full-color device formingthe full-color image to form an image by arranging 4 colors—that is,black, in addition to yellow, magenta and cyan, the market formonochrome images is very large, and black pigment is an indispensablematerial for electrophotography. After the black pigment is mixed,kneaded and dispersed with a resin, they are pulverized and classifiedto be arranged into a desired particle size, inorganic particles ororganic particles are treated by external additives, if necessary, suchas imparting of fluidity, imparting of charge property, and adjustmentof resistance to be used as a toner. As the black pigment, carbon blackparticle powder as a non-magnetic toner, magnetite powder particles as amagnetic toner, or the like have been widely used.

However, there has been a problem in that the carbon black particlepowder, being ultra fine particles, must be very carefully treatedduring production of the toner from the viewpoint of safety andsanitation. Further, since it is bulky powder, there has been a problemin that handling property and fabrication property are bad. Furthermore,although carbon black has very high masking rate and is a materialhaving a high degree of blackness, viscosity increases in accordancewith the added amount due to a filler effect, and therefore there hasbeen a problem in that fixing property is lowered.

As for the magnetite powder particles, there have been problems in thatcoagulation force between particles is strong, dispersibility is bad,and fabrication property and stability of resistance when formed into atoner and charge property are bad, and the like. When the magnetitepowder particles are used under a high temperature condition in theproduction process of the toner and the fixing process in a printer orthe like, the color changes from black to brown, and therefore there hasbeen a problem in usage as a black colorant. Hematite powder particlesare mentioned as a weak magnetic material or non-magnetic materialhaving good handling property. However, there have been problems in thatthey have a low degree of blackness and it is difficult to obtainsufficient image density.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an electrophotographictoner which has good fabrication property and excellent developingproperty, and can form an image having a sufficient density andexcellent fixing property by using a black pigment with substantiallyweak magnetic or non-magnetic property and having a predeterminedparticle size as a coloring material for a toner; an electrophotographicdeveloper using the same; an image forming device and an image formingmethod.

The electrophotographic toner of the invention for achieving the objectof the invention comprises: a binder resin; and particles containingmanganese and iron and having a hematite structure, wherein themanganese content is 3 to 30% by weight, an average particle size is0.01 to 2.0 μm, and saturation magnetization (σs) is 2 emu/g or less, inthe particles. The electrophotographic developer of the invention forachieving the object of the invention comprises at least theelectrophotographic toner of the invention. The electrophotographicimage forming device of the invention for achieving the object of theinvention has at least an electrostatic latent image holding member, anelectrostatic latent image forming means which forms an electrostaticlatent image on the electrostatic latent image holding member, adeveloping means which stores the electrophotographic developer of theinvention and develops the electrostatic latent image to form a visibleimage, and a transfer means which transfers the visible image onto atransfer material.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[Electrophotographic Toner]

The electrophotographic toner of the present invention containspredetermined particles and a binder resin, and other components, ifnecessary.

Particles

The particles contain manganese and iron, and have a hematite structure.The manganese content is 3 to 30% by weight, the average particle sizeis 0.01 to 2.0 μm, and saturation magnetization (as) is 2 emu/g or less,in the particles.

In the particles, the manganese content is preferably 10 to 30% byweight and more preferably 20 to 25% by weight.

When the content is less than 3% by weight, the degree of blackness inthe electrophotographic toner is lowered, and on the other hand, when itexceeds 30% by weight, it is not preferable because the degree ofbrownness becomes stronger.

In the particles, the average particle size is preferably 0.05 to 1.0 μmand more preferably 0.1 to 0.8 μm.

When the average particle size exceeds 2 μm, the dispersion diameterbecomes large when making a toner, and sufficient degree of blacknesscannot be obtained. On the other hand, the smaller the average particlesize, the better it is. However, for the average particle size to beless than 0.01 μm, cracking process and classification process arerequired, which makes the cost very high. Accordingly, in some cases, itis not practical to use it as a colorant for the toner. Therefore, it ispreferably 0.01 μm or more in practical use.

In the invention, the average particle size is determined by calculatingan average radius from the area of one particle for particles that areobserved by an electron microscope (SEM) using image analysis equipmentand determining the particle size, and 10 or more of n number arecounted by similar work to be determined as an average value.

In the particles, it is preferable that the saturation magnetization(as) has substantially weak magnetism or non-magnetism property.Specifically, it is preferably 1.5 emu/g or less, and more preferably 1emu/g or less.

In the invention, “saturation magnetization (as)” is a value measured ata magnetic field of 10 KOe in powder condition.

<<Preparation Method of Particles>>

The preparation method of the particles is not specifically limited, butthe method described below is specifically preferred. For example, Mn orMn and iron are added to a suspension containing magnetite particles, ina state of an aqueous solution. The suspension is oxidized by heating,and exists in a state in which an Mn compound or an Mn compound and anFe compound are homogeneously mixed, or a condition in which the surfaceof the magnetite particles is coated by existence of an Mn compound oran Mn compound and an Fe compound.

By washing mixture particles of the Mn compound-Fe compound-magnetite orthe like in the suspension with water, drying, and calcining them at atemperature range of 600° C. to 1100° C., black particles withsubstantially weak magnetism or non-magnetism property having a hematitestructure in which the saturation magnetization (σs) is 2.0 emu/g orless, Mn is a solid solution, and iron is a main component, can beobtained efficiently.

In the invention, the temperature of calcination by heating whenpreparing the particles is preferably the above-mentioned temperaturerange, namely 600 to 1100° C. and more preferably 700° to 1000° C.

When the temperature of calcination by heating is less than 600° C., themagnetite particles are hardly changed to the hematite structure, andmagnetism is easily maintained. On the other hand, when it exceeds 1100°C., in some cases, the desired particle size cannot be obtained due tocoagulation of particles.

<<Content of Particles>>

The content of the particles in the electrophotographic toner of theinvention is not specifically limited. However, it is preferably 10 to70% by weight, more preferably 15 to 50% by weight and furtherpreferably 20 to 40% by weight.

When the content is less than 10% by weight, in some cases, sufficientdegree of blackness cannot be obtained. On the other hand, when itexceeds 70% by weight, in some cases, fixing property is lowered.

Binder Resin

The binder resin is not specifically limited, and there are variousknown thermoplastic resins comprising a natural or synthetic polymer. Apreferable example includes a resin having a weight average molecularweight of approximately 4000 to 100000 and a melting point ofapproximately 90 to 150° C., or the like. Specific examples of thebinder resin include an epoxy resin, a styrene-acryl resin, apolyether-polyol resin, a polyethylene, a cycloolefin resin such as apolypropylene, a polyacryl resin, a polyamide resin, a polyester resin,a polyvinyl resin, a polyurethane resin, a polybutadiene resin or thelike. These may be used alone, or two or more may be used incombination. Among these, a polyester resin or the like are particularlypreferable.

The content of the binder resin in the electrophotographic toner of theinvention is not specifically limited; however, it is preferably 30 to95% by weight and more preferably 40 to 90% by weight.

Other Components

Other components are not specifically limited and can be selectedsuitably among known articles according to the purpose. Examples includea colorant other than the predetermined particles, an infrared absorbingagent, a charge controlling agent, a fluidity improving agent, waxes, afixation aid, a metal soap, a cleaning activator, a surfactant or thelike.

Colorant

Further desired coloring property can be realized by mixing variousknown colorants for respective colors such as yellow, magenta, cyan andblack in the electrophotographic toner of the invention, other than theabove-mentioned predetermined particles containing the manganese andiron and having the hematite structure.

The colorant is not specifically limited and can be selected suitablyamong known articles according to the purpose. Examples of the colorantinclude a yellow colorant, a magenta colorant, a cyan colorant, a blackcolorant or the like. Specific examples include lamp black, iron black,navy blue, a nigrosin dye, aniline blue, Calco Oil Blue, Du Pont OilRed, quinoline yellow, methylene blue chloride, phthalocyanine blue,phthalocyanine green, Hanza Yellow, Rhodamine 6C lake, chrome yellow,quinacridone, benzidine yellow, malachite green, malachite greenhexalate, rose bengal, naphthol, carmine, quinacridone, a mono-azo dyeand pigment, a dis-azo dye and pigment, a tris-azo dye pigment, and thelike.

Examples of the yellow colorant include a condensed azo compound, anisoindolinone compound, an anthraquinone compound, an azo metal complex,a methine compound, an arylamide compound, and the like. Specificpreferable examples, include C.I. Pigment Yellows 12, 13, 14, 15, 17,62, 74, 83, 93, 94, 95, 109, 110, 111, 128, 129, 147, 168, 180, 185, orthe like.

Examples of the magenta colorant include a condensed azo compound, adiketopyrrolopyrole compound, anthraquinone, a quinacridone compound, abase dye lake compound, a naphthol compound, a benzimidazol compound, athioindigo compound, a perylene compound or the like. Specifically,preferably they include C.I. Pigment Reds 2, 3, 5, 6, 7, 23, 48:2, 48:3,48:4, 57:1, 81:1, 122, 144, 146, 166, 169, 177, 184, 185, 202, 206, 220,221, 254 or the like.

Examples of the cyan colorant include a copper phthalocyanine compoundand its derivative, an anthraquinone compound, abase dye lake compoundor the like. Specifically, preferably they include C.I. Pigment Blues 1,7, 15, 15:1, 15:2, 15:3, 15:4, 60, 62, 66 or the like.

These colorants may be used alone, or two or more may be used incombination.

The content of the colorant in the electrophotographic toner of theinvention is preferably 0.1 to 20% by weight and more preferably 0.2 to10% by weight.

Infrared Absorbing Agent

The infrared absorbing agent may be a material having at least one ormore of intense optical absorption peaks at near infrared region of 750to 1200 nm, and may be either of an inorganic infrared absorbing agentor an organic infrared absorbing agent.

Examples of the inorganic infrared absorbing agent include lanthanoidcompounds such as ytterbium oxide and ytterbium phosphate, indium tinoxide, stannic oxide or the like.

Examples of the organic infrared absorbing agent include an aminiumcompound, a diimmonium compound, a naphthalocyanine compound, a cyaninecompound, a polymethine compound or the like.

These colorants may be used alone, or two or more may be used incombination.

The content of the infrared absorbing agent in the electrophotographictoner of the invention is preferably 0.1 to 5% by weight and morepreferably 0.3 to 3% by weight.

When the content is less than 0.1% by weight, the electrophotographictoner may not be able to be fixed, and on the other hand, when itexceeds 5% by weight, the color of an image formed may be turbid.

Charge Controlling Agent

The charge quantity of the electrophotographic toner of the inventioncan be easily controlled within a desired range by using the chargecontrolling agent. As the charge controlling agent, a positive polarcharge controlling agent, a negative polar charge controlling agent orthe like are used suitably by applying a positive charge or a negativecharge to the binder resin. Examples of the positive polar chargecontrolling agent include a nigrosin dye, a quaternary ammonium salt, atriphenyl methane derivative or the like. Examples of the negative polarcharge controlling agent include a metal-containing azo complex, a zincnaphthoate complex, a zinc salicylate complex, a calixarene compound orthe like. These may be used alone, or two or more may be used incombination.

Fluidity Improving Agent

The fluidity improving agent is not specifically limited and can beselected suitably among known articles according to the purose. Examplesof the fluidity improving agent include inorganic fine particles such aswhite particles or the like.

The primary average particle size of the inorganic fine particles ispreferably 5 nm to 2 μm and more preferably 5 nm to 500 nm. The specificsurface area of the inorganic fine particles by a BET method ispreferably 20 to 500 m²/g. Examples of the inorganic fine particleinclude silica fine powder, alumina, titanium oxide, barium titanate,magnesium titanate, calcium titanate, strontium titanate, zinc oxide,silica, clay, mica, wollastonite, diatom earth, chromium oxide, ceriumoxide, iron oxide red, antimony trioxide, magnesium oxide, zirconiumoxide, barium sulfate, barium carbonate, calcium carbonate, siliconcarbide, silicon nitride or the like.

These may be used alone, or two or more may be used in combination.Among these, silica fine powder is preferable, and a combination ofsilica fine powder, a titanium compound, resin fine powder and aluminaor the like is also preferable.

The content of the fluidity improving agent in the electrophotographictoner of the invention is preferably 0.01 to 5% by weight and morepreferably 0.01 to 2.0% by weight.

Cleaning Activator

The cleaning activator is not specifically limited and can be suitablyselected among known articles according to the purpose. Examples of thecleaning activator include a metal salt of higher fatty acid which isrepresented by zinc stearate or the like, the fine particle powder of afluorine-base polymer or the like.

Surfactant

An example of the surfactant includes a nonionic surfactant or the like.

<Production Method of Electrophotographic Toner>

The production method of the electrophotographic toner of the inventionis not specifically limited and can be suitably selected among knownmethods according to the purpose. An example of the production methodincludes a mechanically pulverizing method of producing thepredetermined particles by homogeneously mixing together with toner rawmaterials such as a binder resin, a wax component, a colorant (pigmentor the like) other than the predetermined particles and variousadditives (an infrared absorbing agent, a charge controlling agent, amagnetic body or the like) by using a mixing apparatus such as a ballmill and a Henschel mixer, then melting and kneading by using a heatkneading apparatus such as a heating roll, a pressuring kneader and anextruder, dispersing in a resin a metal compound, a pigment, a dye, amagnetic body or the like to solidify them by cooling, then pulverizingthem using a pulverizing apparatus such as a jet mill, and classifyingthe pulverized articles to a desired particle size distribution by awind power classification device or the like, and the like. Further, thepredetermined particles can be obtained by adjusting fluidity and chargeproperty by carrying out surface treatment of silica fine powder or thelike, if necessary.

<Magnetism of Electrophotographic Toner>

The electrophotographic toner of the invention differs from a magnetictoner which is adsorbed on a developer holding member by magneticretention force. Specifically, as the magnetism of theelectrophotographic toner of the invention, it is preferable that thesaturation magnetization (as) has substantially weak magnetic ornon-magnetic property which is 2 emu/g or less, 0.5 emu/g or less ismore preferable and 0.1 emu/g or less is further preferable.

[Developer for Electrophotographic Toner]

The electrophotographic developer of the invention contains at least theelectrophotographic toner of the invention, and contains othercomponents which are selected suitably, if necessary.

The electrophotographic developer may be a non-magnetic monocomponentdeveloper comprising the electrophotographic toner, and may be atwo-component developer containing the electrophotographic toner and acarrier. However, when it is used for a high-speed printer or the likecorresponding to the recent improvement in information processing speed,the two-component developer is preferable from the viewpoint of longeroperational life or the like.

Carrier

The carrier is not specifically limited and can be selected suitablyaccording to the purpose. However, those having a core and a resin layercoating the core are preferable.

As a material for the core, for example, a manganese-strontium(Mn—Sr)-base material, a manganese-magnesium (Mn—Mg)-base material orthe like, being 50 to 90 emu/g are preferable. From the viewpoint ofsecuring image density, low-resistance materials such as iron powder(100 emu/g or more) and magnetite (75 to 120 emu/g) are preferable. Fromthe viewpoint that hit to a photoreceptor being in a state in which thetoner is eared can be weakened which is advantageous in enhancing imagequality, weak magnetic materials such as copper-zinc (Cu—Zn)-base (30 to80 emu/g) are preferable. These may be used alone, or two or more may beused in combination.

The particle size of the core is preferably an average particle size of10 to 150 μm, and 40 to 100 μm is more preferable.

When the average particle size is less than 10 μm, an amount of finepowder increases in the distribution of carrier particles, andmagnetization per particle decreases, which may cause carrier scatteringin some cases. When it exceeds 150 μm, specific surface area decreases,and scattering of a toner may occur, and in particular, reproduction ofa solid portion may deteriorate in some cases. The average particle sizeis a value determined by the same measurement method of an averageparticle size mentioned above.

The material of the resin layer is not specifically limited and can beselected suitably among known materials according to the purpose.However, from the viewpoint of durability, long life or the like,preferable examples of the material of the resin layer include siliconeresins such as a silicone-base resin, an acryl-modified silicone-baseresin, and a fluorine-modified silicone-base resin. These may be usedalone, or two or more may be used in combination.

The resin layer can be formed, for example, by dissolving the siliconeresin or the like in a solvent to prepare a coating solution, thenuniformly coating the coating solution on the surface of the core byknown methods such as an immersion method, a spray method, and a brushcoating method, drying it, and then carrying out baking, and the like.

The solvent is not specifically limited and can be selected suitablyaccording to the purpose. However, examples of the solvent includetoluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, cellosolvebutyl acetate or the like.

The baking may be an external heating system, or may be an internalheating system. Examples include a method using a fixed electricfurnace, a fluidized electric furnace, a rotary electric furnace, aburner furnace or the like, a method using microwave, and the like.

The ratio (the coating amount of a resin) in the carrier of the resinlayer is preferably 0.01 to 5.0% by weight based on the total amount ofthe carrier.

When the ratio (the coating amount of a resin) is less than 0.01% byweight, a uniform resin layer cannot be formed on the surface of thecore in some cases. When it exceeds 5.0% by weight, the resin layerbecomes too thick, granulation of mutual carriers is generated, anduniform carrier particles cannot be obtained in some cases.

When the electrophotographic developer is the two-component developer,the content of the carrier in the two-component developer is notspecifically limited and can be selected suitably according to thepurpose. However, for example, 90 to 98% by weight is preferable, and 93to 97% by weight is more preferable.

Since the electrophotographic developer of the invention contains theelectrophotographic toner of the invention, fabrication property is goodand an image with sufficient density can be formed. Theelectrophotographic developer of the invention can be used suitably toform an image by known various electrophotographic methods such as anon-magnetic monocomponent developing method and a two-componentdeveloping method, and in particular, can be used suitably for the imageforming method and the image forming device of the invention to bediscussed hereinafter.

[Image Forming Method and Image Forming Device]

The image forming method of the invention includes at least anelectrostatic latent image forming step, a developing step, and atransfer step, and preferably further includes a fixing step, and mayinclude other steps which are selected suitably, if necessary, such asan electricity removal step, a cleaning step, a recycling step, and acontrolling step.

The image forming device of the invention has at least an electrostaticlatent image holding member, an electrostatic latent image formingmeans, a developing means, and a transfer means, and further preferablyhas a fixing means, and may have other means which are selectedsuitably, if necessary, such as an electricity removal means, a cleaningmeans, a recycling means, and a controlling means.

The image forming method of the invention can be carried out suitably bythe image forming device of the invention, the electrostatic latentimage forming step can be preferably carried out by the electrostaticlatent image forming means, the developing step can be carried out bythe developing means, the transfer step can be carried out by thetransfer means, the fixing step can be carried out by the fixing means,and the other steps can be carried out by the other means.

Electrostatic Latent Image Forming Step and Electrostatic Latent ImageForming Means

The electrostatic latent image forming step is a step of forming anelectrostatic latent image on a electrostatic latent image holdingmember.

As the electrostatic latent image holding member (occasionally referredto as “photoconductive insulator” and “photoreceptor”), the material,shape, structure, size, or the like thereof are not specificallylimited, and may be selected suitably among known articles. However,preferable shape is a drum shape. Examples of the material includeinorganic photoreceptors bodies such as amorphous silicon and selenium,organic photoreceptors such as a polysilane and phthalocyanine, or thelike.

The formation of the electrostatic latent image can be carried out by,for example, uniformly charging the surface of the electrostatic latentimage holding member and then exposing it imagewise, and can be carriedout by the electrostatic latent image forming means.

The electrostatic latent image forming means is provided with at least acharge device which uniformly charges the surface of the electrostaticlatent image holding member, and an exposure device which imagewiseexposes the surface of the electrostatic latent image holding member.

The charge can be carried out by, for example, applying a voltage on thesurface of the electrostatic latent image holding member using thecharge device.

The charge device is not specifically limited and can be selectedsuitably according to the purpose. However, examples of the chargedevice include a known contact type charge device equipped with aconductive or semiconductive roll, brush, film, rubber blade or thelike, a non-contact type charge device utilizing corona discharge suchas a corotron and a scorotron, and the like.

The exposure can be carried out by, for example, exposing the surface ofthe electrostatic latent image holding member imagewise by using theexposure device.

The charge device is not specifically limited as long as it canimagewise expose the surface of the charged electrostatic latent imageholding member by using the charge device, and can be selected suitablyaccording to the purpose. Examples of the exposure device includevarious exposure devices such as a copy optics, a rod lens array system,a LED system, a laser optics system, and a liquid crystal shutter opticssystem.

Further, in the invention, an optical rear system which carries outexposure imagewise from the rear side of the electrostatic latent imageholding member may be used.

Developing Step and Developing Means

The developing step is a step of developing the electrostatic latentimage using the electrophotographic developer, and forming a visibleimage.

The formation of the visible image can be carried out by, for example,developing the electrostatic latent image using the electrophotographicdeveloper, and can be carried out by the developing means.

The developing means stores the electrophotographic developer, and hasat least a developing unit which imparts the electrophotographicdeveloper to the electrostatic latent image in contact or innon-contact.

The developing unit may be a dry developing system, may be a mono colordeveloping unit, or may be a multi-color developing unit. However,preferable examples of the developing unit include those having astirrer which stirs the electrophotographic developer by friction to becharged, and a magnet roller capable of rotating, and the like.

For example, in the developing unit, the electrophotographic toner andthe carrier are stirred by mixing, the electrophotographic toner ischarged by the friction at that time and kept on the surface of therotating magnet roller in an earring state, and a magnet brush isformed. Since the magnet roller is arranged near the electrostaticlatent image holding member (photoreceptor), a portion of theelectrophotographic toner which composes the magnet brush formed on thesurface of the magnet roller is moved to the surface of theelectrostatic latent image holding member (photoreceptor) by electricabsorbing force. As a result, the electrostatic latent image isdeveloped by the electrophotographic toner, and a visible image by thetoner is formed on the surface of the electrostatic latent image holdingmember (photoreceptor).

While the developer stored in the developing unit is theelectrophotographic developer of the invention, the electrophotographicdeveloper may be a monocomponent developer or a two-component developer.The toner contained in the electrophotographic developer is theelectrophotographic toner of the invention. A black toner is generallyused in the case of development for mono color, and a chromatic colortoner selected from a magenta toner, a yellow toner, and a cyan toner isused in addition to the black toner in the case of development formulti-colors. In the case of full colors, a black toner, a magentatoner, a yellow toner, and a cyan toner are used.

Transfer Step and Transfer Means

The transfer step is a step of transferring the visible image to atransfer material.

The transfer can be carried out by, for example, using a transfer chargedevice which is reverse polar against the electrophotographic toner, forthe visible image, and by a transfer means.

The transfer means has at least a transfer device which peals andcharges the visible image formed on the electrostatic latent imageholding member (photoreceptor), to the transfer material.

Examples of the transfer device include a corona transfer device bycorona discharge, a transfer belt, a transfer roller, a pressuringtransfer roller, an adhesive transfer device or the like.

The transfer material is not specifically limited, and can be selectedsuitably among known recording media (a recording paper).

Fixing Step and Fixing Means

The fixing step is a step of fixing the transfer image transferred ontothe transfer material using the fixation device.

The fixation may be, for example, fixation by heating and pressuring thetransfer image transferred onto the transfer material, using a heatingfixation roller. However, optical fixation is preferable, and can becarried out by the fixing means.

The optical fixation can be performed, for example, by carrying outoptical irradiation against the transfer image transferred onto thetransfer material, using an optical fixation device, and can be carriedout by the optical fixing means.

As the optical fixing means, a flash lamp irradiating infrared rays ispreferable.

The flash lamp is not specifically limited, and can be selected suitablyaccording to the purpose. Preferable examples include an infrared lamp,a xenon lamp or the like.

Flash energy in the optical fixation is preferably approximately 1 to 3J/cm².

When the flash energy is less than 1 J/cm², fixation cannot be carriedout well in some cases. On the other hand, when it exceeds 3 J/cm²,toner void, scorching of papers or the like may occur.

The electricity removal step is a step of removing electricity bycarrying out whole surface exposure or by applying electricity removalbias to the electrostatic latent image holding member, and can becarried out suitably by the electricity removal means.

The electricity removal means is not specifically limited as long as itcan carry out exposure or apply electricity removal bias to theelectrostatic latent image holding member, and can be selected suitablyamong known electricity removal devices.

The cleaning step is a step of removing the electrophotographic tonerremaining on the electrostatic latent image holding member, and can becarried out suitably by the cleaning means.

The cleaning means is not specifically limited as long as it can removethe electrophotographic toner remaining on the electrostatic latentimage holding member, and can be selected suitably among known cleaners.Preferable examples of the cleaner include a magnetic brush cleaner, anelectrostatic brush cleaner, a magnetic roller cleaner, a blade cleaner,a brush cleaner, web cleaner, or the like.

The recycling step is a step of recycling the electrophotographic tonerwhich is removed by the cleaning step, into the developing means, andcan be carried out suitably by the recycling means.

The recycling means is not specifically limited, and may be knownconveying means or the like.

The controlling means is not specifically limited as long as it cancontrol the motion of the respective means, and can be selected suitablyaccording to the purpose. Examples of the controlling means includeequipment such as a sequencer and a computer.

In the image forming method of the invention, an electrostatic latentimage is formed on the electrostatic latent image holding member in theelectrostatic latent image forming step. The electrostatic latent imageis developed by the electrophotographic developer in the developing stepto form a visible image. In the transfer step, the visible image istransferred onto the transfer material. In the fixing step, the transferimage transferred is fixed onto the transfer material. As a result, animage is formed on the transfer material. As a result, an image is fixedand formed at extremely high speed on the transfer material.

Further, in the image forming device of the invention, the electrostaticlatent image forming means forms the electrostatic latent image on theelectrostatic latent image holding member. The developing means storesthe electrophotographic developer, develops the electrostatic latentimage, and forms the visible image. The transfer means transfers thevisible image onto the transfer material. The fixing means fixes thetransfer image transferred onto the transfer material. As a result, animage is fixed and formed at extremely high speed on the transfermaterial.

Since the electrophotographic developer of the invention containing theelectrophotographic toner of the invention is used as theelectrophotographic developer in the image forming device and imageforming method, an image excellent in image quality and chroma can beformed efficiently.

Although the image forming device is not specifically limited, it ispreferably a high speed developing type in which processing speed isapproximately 1100 mm/s, and is preferably a device having aphotoreceptor comprising amorphous silicon.

EXAMPLES

Hereinafter, the present invention will be described in further detailwith reference to Examples. However, the invention is not limited tothese Examples at all.

Examples 1 to 12, Comparative Examples 1 to 7

Preparation of Black Particles (Pigments 1 to 10)

Mixture particles of an Mn compound-an Fe compound-magnetite are washedwith water, dried and calcined by heating at a high temperature of 850°C. to prepare the respective black particles (pigments 1 to 10) shown inTable 1. The calcination temperatures when calcining the respectiveblack particles by heating, Mn contents (% by weight) in the respectiveblack particles, particle size (average particle size (μm)), andsaturation magnetization (as (emu/g)) measured at a magnetic field of 10KOe in powder state are respectively shown in Table 1. Further, thedetails of other pigments (a magnetite pigment, a hematite pigment, acarbon black pigment, a cyan pigment, a yellow pigment, and a magentapigment) are similarly shown in Table 1. TABLE 1 Pigment Pigment PigmentPigment Pigment Pigment Pigment Pigment Pigment Pigment Material 1 2 3 45 6 7 8 9 10 Mn content wet % 22 3 30 1 40 22 22 22 22 22 Particle sizeμm 0.3 0.3 0.3 0.3 0.3 0.01 2.0 4.0 0.3 0.3 σs emu/g 0.6 0.6 0.6 0.6 0.60.6 0.6 0.6 2 5 Calcination ° C. 850 850 850 850 850 850 1100 1200 600300 temperature Magnetite Hematite Yellow Magenta Material pigmentpigment Carbon black Cyan pigment pigment pigment — Mn content wet % 0 0— — — — — Particle size μm 0.3 0.3 Primary particle — — — — size 25 nmσs emu/g 50 2 — — — — — Calcination ° C. — — — — — — — temperature

Preparation of Electrophotographic Toner

The electrophotographic toners 1 to 19 shown in Table 2 are prepared bythe compounding amount of components shown in Table 2.

In the preparation, a polyester resin (manufactured by Kao Corporation)is used as a binder resin, N-01 (trade name, manufactured by OrientChemical Industries, Ltd.) is used as a positive polar chargecontrolling agent, and polypropylene-base wax NP105 (trade name,manufactured by Mitsui Chemicals Inc.) is used as wax. After therespective components are charged in a Henschel mixer to carry outpreliminary mixing, the respective components are melt-kneaded to bedispersed and solidified in a binder resin. They are pulverized andclassified to obtain a positive charge black toner mother body having anaverage particle size of 9 μm. To the toner mother body obtained, 0.8parts by weight of hydrophobic silica is externally added to obtain therespective electrophotographic toners 1 to 19.

A polyester resin in which the ethylene oxide of bisphenol A is a maindiol component and terephthalic acid and trimellitic acid are maincarboxylic acid components is used.

Preparation of Electrophotographic Developers 1 to 19

The electrophotographic toners 1 to 19 are respectively compounded withferrite carrier (an average particle size of 70 μm) at a tonerconcentration of 4.5% by weight to obtain the electrophotographicdevelopers 1 to 19 shown in Table 2. The electrophotographic developers1 to 3 obtained are respectively used as the electrophotographicdevelopers of Examples 1 to 3, the electrophotographic developers 4 to 5are respectively used as the electrophotographic developers ofComparative Examples 1 to 2, the electrophotographic developers 6 to 7are respectively used as the electrophotographic developers of Examples4 to 5, the electrophotographic developer 8 is used as theelectrophotographic developer of Comparative Example 3, theelectrophotographic developer 9 is used as the electrophotographicdeveloper of Example 6, the electrophotographic developers 10 to 13 arerespectively used as the electrophotographic developers of ComparativeExamples 4 to 7, the electrophotographic developers 14 to 19 arerespectively used as the electrophotographic developers of Examples 7 to12, and the respective evaluations shown below are carried out. TABLE 2Electrophotographic toner Electro- Electro- Electro- Electro- Electro-Electro- Electro- Electro- Electro- Electro- photographic photographicphotographic photographic photographic photographic photographicphotographic photographic photographic toner 1 toner 2 toner 3 toner 4toner 5 toner 6 toner 7 toner 8 toner 9 toner 10 Material (parts bymass) (parts by mass) (parts by mass) (parts by mass) (parts by mass)(parts by mass) (parts by mass) (parts by mass) (parts by mass) (partsby mass) Binder resin Manufactured by Kao 67 67 67 67 67 67 67 67 67 67(polyester resin) Corporation Colorant Item 1 Pigment 1 Pigment 2Pigment 3 Pigment 4 Pigment 5 Pigment 6 Pigment 7 Pigment 8 Pigment 9Pigment 10 30 30 30 30 30 30 30 30 30 30 Item 2 — — — — — — — — — — N-01(charge Manutactured by 2 2 2 2 2 2 2 2 2 2 controlling agent) OrientChemical Industries, Ltd. NP105 Manufactured by 1 1 1 1 1 1 1 1 1 1(polypropylene): Mitsui Chemicals Inc. number average molecular weight10000 Toner σs (ems/g) <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 1.1 3performance Particle size (μm) 9 9 9 9 9 9 9 9 9 9 Electrophotographicdeveloper Developer 1 Developer 2 Developer 3 Developer 4 Developer 5Developer 6 Developer 7 Developer 8 Developer 9 Developer 10 (Example 1)(Example 2) (Example 3) (Comparative (Comparative (Example 4) (Example5) (Comparative (Example 6) (Comparative Example 1) Example 2) Example3) Example 4) Toner concentration (% by mass) 4.5 4.5 4.5 4.5 4.5 4.54.5 4.5 4.5 4.5 Electrophotographic toner Electro- Electro- Electro-Electro- Electro- Electro- Electro- Electro- Electro- photographicphotographic photographic photographic photographic photographicphotographic photographic photographic toner 11 toner 12 toner 13 toner14 toner 15 toner 16 toner 17 toner 18 toner 19 Material (parts by mass)(parts by mass) (parts by mass) (parts by mass) (parts by mass) (partsby mass) (parts by mass) (parts by mass) (parts by mass) Binder resinManufactured by Kao 67 67 87 66 65.5 87 27 93 17 (polyester resin)Corporation Colorant Item 1 Magnetite Hematite pigment Carbon blackPigment 7 Pigment 7 Pigment 1 Pigment 1 Pigment 1 Pigment 1 pigment, 3030 10 30 30 10 70 5 80 Item 2 — — — Cyan 1 Cyan, Yellow, Magenta, — — —— — — — 0.5 wt % respectively — — — — N-01 (charge Manutactured by 2 2 22 2 2 2 2 2 controlling agent) Orient Chemical Industries, Ltd. NP105Manufactured by 1 1 1 1 1 1 1 1 1 (polypropylene): Mitsui Chemicals Inc.number average molecular weight 10000 Toner σs (ems/g) 20 <0.1 <0.1 <0.1<0.1 <0.1 0.5 <0.1 0.6 performance Particle size (μm) 9 9 9 9 9 9 9 9 9Electrophotographic developer Developer 11 Developer 12 Developer 13Developer 14 Developer 15 Developer 16 Developer 17 Developer 18Developer 19 (Comparative (Comparative (Comparative (Example 7) (Example8) (Example 9) (Example 10) (Example 11) (Example 12) Example 5) Example6) Example 7) Toner concentration (% by mass) 4.5 4.5 4.5 4.5 4.5 4.54.5 4.5 4.5

In Table 2, “<0.1” indicates that saturation magnetization (σs) is lessthan 0.1 ems/g.

<Printing Test>

The electrophotographic developers 1 to 19 obtained are mounted on themodified machine of a printer (trade name: F6764, manufactured byFujitsu Co., Ltd.), irradiated with xenon flash light having highluminescence intensity at a wavelength range of 700 to 1500 nm, and thetoners are fixed on plain paper (trade name: “NIP-1500LT”, manufacturedby Kobayashi Kirokushi Co., Ltd.) to form an image.

<<Measurement of Printing Density (OD) and Evaluation of Image Density>>

The printing density (OD) in the image obtained is measured by usingMacbeth RD 918 (trade name, manufactured by Macbeth Inc.), OD when thescreen attached amount of 1 inch image is 0.5 mg/cm² is measured as theprinting density, and the image density is evaluated in accordance withthe OD criteria described below. Results are shown in Tables 3 to 4.

OD Criteria

-   -   OD≧1.3⊚    -   1.3>OD≧1.2◯    -   1.2>OD≧1.1Δ    -   OD<1.1×        <<Measurement and Evaluation of Value a and Value b>>

Value a and value b are measured for the image obtained usingSpectrodensitmeter (trade name: X-Rite 938, manufactured by X-RiteLtd.), and evaluated based on the evaluation criteria described below.Results are shown in Tables 3 to 4.

Evaluation Criteria of Value a and Value b

-   -   a≦1 and b≦1⊚    -   a≦3 and b≦3◯    -   a≦5 and b>5Δ    -   a>5 or b>5×        <<Tape Pealing Test and Evaluation of Fixing Property>>

A tape pealing test shown below is carried out for the image obtained,and the toner fixation rate is evaluated according to the evaluationcriteria described below.

Firstly, the image printing density on plain paper on which a tonerimage is fixed is measured as optical density. Then, after a pealingtape (trade name: “Scotch Mending Tape”, (manufactured by Sumitomo 3MLtd.)) is adhered on the toner image of the plain paper, the pealingtape is pealed, and the optical density on the plain paper after pealingis measured. Taking the image printing density on plain paper beforepealing as 100, the image printing density on plain paper after pealingis represented in percentage and is referred to as the toner fixationrate, by which the fixing property of the image is evaluated. Resultsare shown in Tables 3 to 4. The Macbeth RD 918 is used for measurementof the optical density.

Evaluation Criteria

-   -   When the image printing density is 5% or less (namely, the        fixation rate is 95% or more) ⊚    -   When the image printing density exceeds 5% and is 10% or less        (namely, the fixation rate is 90% or more and less than 95%) ◯    -   When the image printing density exceeds 10% and is 20% or less        (namely, the fixation rate is 80% or more and less than 90%) Δ    -   When the image printing density exceeds 20% (namely, the        fixation rate is less than 80%) ×        <<Evaluation of Developing Property>>

Evaluation is carried out in accordance with the evaluation criteriadescribed below by potential difference (the setting value of developingbias potential (Vb)) when the adhered amount at 1 inch screen is 0.5mg/cm². Results are shown in Tables 3 to 4. The difference betweensurface potential (Vs) and the developing bias potential (Vb) isadjusted by constantly moving in parallel at 250 V.

Evaluation Criteria

-   -   300 V or less ⊚    -   More than 300 V, and 400 V or less ◯    -   More than 400 V, and 600 V or less Δ

More than 600 V × TABLE 3 Example, Comparative Example Example 1 Example2 Example 3 Example 4 Example 5 Electrophotographic ElectrophotographicElectrophotographic Electrophotographic ElectrophotographicElectrophotographic developer developer 1 developer 2 developer 3developer 6 developer 7 Toner 4.5 4.5 4.5 4.5 4.5 concentration (% bymass) OD ⊚ Δ ◯ ⊚ Δ Fixing property ⊚ ⊚ ⊚ ⊚ ◯ (%) Property of ⊚ ◯ Δ ⊚ Δvalues a and b Developing ⊚ ⊚ ⊚ ⊚ ◯ property Example, ComparativeComparative Comparative Comparative Comparative Example Example 6Example 1 Example 2 Example 3 Example 4 ElectrophotographicElectrophotographic Electrophotographic ElectrophotographicElectrophotographic Electrophotographic developer developer 9 developer4 developer 5 developer 8 developer 10 Toner 4.5 4.5 4.5 4.5 4.5concentration (% by mass) OD ◯ X Δ X X Fixing property ⊚ ⊚ ⊚ Δ ⊚ (%)Property of ◯ Δ X Δ Δ values a and b Developing Δ ◯ Δ Δ X property

TABLE 4 Example, Comparative Example Example 7 Example 8 Example 9Example 10 Example 11 Electrophotographic Fixation Fixation FixationFixation Fixation developer property 14 property 15 property 16 property17 property 18 Toner concentration 4.5 4.5 4.5 4.5 4.5 (% by mass) OD ◯◯ Δ ◯ Δ Fixing property (%) ⊚ ⊚ ⊚ Δ ⊚ Property of values ◯ ◯ Δ ⊚ Δ a andb Developing property ⊚ ⊚ ⊚ Δ ◯ Example, Comparative ComparativeComparative Comparative Example Example 12 Example 5 Example 6 Example 7Electrophotographic Fixation Fixation property Fixation propertyFixation property developer property 19 11 12 13 Toner concentration 4.54.5 4.5 4.5 (% by mass) OD ◯ X X ⊚ Fixing property (%) Δ ⊚ ⊚ X Propertyof values ◯ Δ Δ ⊚ a and b Developing property ◯ X ⊚ ◯

According to Tables 3 and 4, the electrophotographic toners in which thepredetermined amount of particles having a hematite structure in whichMn and iron are main components is compounded as a black pigment have agood degree of blackness and are superior in fabrication property. Whenan image is formed by the electrophotographic developer using theseelectrophotographic toners, it is superior in fixing property,developing property, value a and value b.

The preferable modes of the invention are additionally described asfollows.

(Additional Remark 1)

An electrophotographic toner comprising: a binder resin; and particlescontaining manganese and iron and having a hematite structure, whereinmanganese content is 3 to 30% by weight, an average particle size is0.01 to 2.0 μm, and saturation magnetization (as) is 2 emu/g or less, inthe particles.

(Additional Remark 2)

An electrophotographic toner according to Additional remark 1, whereinthe particles are black powder particles obtained by calcining at leastmagnetite particles and a manganese compound by heating at a temperatureof 600 to 1100° C.

(Additional Remark 3)

An electrophotographic toner according to Additional remark 1 or 2,wherein the manganese is manganese which is a solid solution.

(Additional Remark 4)

An electrophotographic toner according to Additional remark 2 or 3,wherein the particles have substantially weak magnetic or non-magneticproperty in comparison with magnetite particles.

(Additional Remark 5)

An electrophotographic toner according to any one of Additional remarks1 to 4, wherein the content of the particles in the electrophotographictoner is 10 to 70% by weight.

(Additional Remark 6)

An electrophotographic toner according to any one of Additional remarks1 to 5, comprising at least any one of colorants of cyan, magenta andyellow.

(Additional Remark 7)

An electrophotographic toner according to any one of Additional remarks1 to 6, wherein the manganese content in the particles is 10 to 30% byweight.

(Additional Remark 8)

An electrophotographic toner according to any one of Additional remarks1 to 7, wherein an average particle size in the particles is 0.01 to 1.0μm.

(Additional Remark 9)

An electrophotographic toner according to any one of Additional remarks1 to 8, wherein the content of the particles in the electrophotographictoner is 15 to 50% by weight.

(Additional Remark 10)

An electrophotographic toner according to any one of Additional remarks1 to 9, wherein saturation magnetization (σs) is 1 emu/g or less.

(Additional Remark 11)

An electrophotographic developer comprising at least theelectrophotographic toner according to any one of Additional remarks 1to 10.

(Additional Remark 12)

An electrophotographic developer according to Additional remark 11containing a carrier.

(Additional Remark 13)

An image forming device comprising at least an electrostatic latentimage holding member, an electrostatic latent image forming means whichforms an electrostatic latent image on the electrostatic latent imageforming holding member, a developing means which stores theelectrophotographic developer according to Additional remark 11 or 12and develops the electrostatic latent image to form a visible image, anda transfer means which transfers the visible image onto a transfermaterial.

(Additional Remark 14)

An image forming device according to Additional remark 13, furthercomprising an optical fixing means which carries out optical fixation ofa transfer image transferred onto the transfer material.

(Additional Remark 15)

An image forming method comprising at least an electrostatic latentimage forming step which forms an electrostatic latent image on anelectrostatic latent image holding member, a developing step whichdevelops the electrostatic latent image using the electrophotographicdeveloper according to Additional remark 11 or 12 and forms a visibleimage, and a transfer step which transfers the visible image onto atransfer material.

(Additional Remark 16)

An image forming method according to Additional remark 15, furthercomprising a fixing step which carries out the optical fixation.

1-5. cancelled.
 6. An electrophotographic toner for a photo-fixing method comprising: a binder resin; and particles containing manganese and iron and having a hematite structure, wherein manganese content is 3 to 30% by weight, an average particle size is 0.01 to 2.0 μm, and saturation magnetization (σs) is 2 emu/g or less, in the particles.
 7. The electrophotographic toner for the photo-fixing method according to claim 6, wherein the particles are black powder particles obtained by calcining at least magnetite particles and a manganese compound by heating at a temperature of 600 to 1100° C.
 8. The electrophotographic toner for the photo-fixing method according to claim 6, wherein the manganese is manganese which is a solid solution.
 9. An electrophotographic developer containing at least the electrophotographic toner for the photo-fixing method according to claim
 6. 10. An image forming device comprising at least an electrostatic latent image holding member, an electrostatic latent image forming means which forms an electrostatic latent image on the electrostatic latent image holding member, a developing means which stores the electrophotographic developer according to claim 9 and develops the electrostatic latent image to form a visible image, and a transfer means which transfers the visible image onto a transfer material.
 11. The electrophotographic toner for the photo-fixing method according to claim 7, wherein the manganese is manganese which is a solid solution.
 12. An electrophotographic developer containing at least the electrophotographic toner for the photo-fixing method according to claim
 7. 13. An electrophotographic developer containing at least the electrophotographic toner for the photo-fixing method according to claim
 8. 